I don't understand
Indicates that the speaker is not understanding the current subject or situation.
ADV
clearly, well
fully, perfectly, quite
I didn't quite understand what the teacher explained about the math problem yesterday.
not really
I don't really understand why she decided to leave her job without telling anyone.
adequately
correctly, properly
My teacher explained the math problem again so I could correctly understand it.
easily, readily
Most people readily understand why children need sleep and rest.
instinctively, intuitively
The child instinctively understood that his mother was upset, even though she didn't say anything.
VERB + UNDERSTAND
be able/unable to, can/could
She was unable to understand why her friend suddenly stopped talking to her.
try to | begin to | be easy to
be difficult to, be hard to
It was hard to understand what the teacher meant by that confusing explanation.
help (to), help sb (to)
PREP
about
Scientists still don't understand much about why some people get allergies.
PHRASES
be commonly/generally/popularly understood
Success is commonly understood to mean having a lot of money and a prestigious job.
be imperfectly/incompletely/poorly understood
Many people find that their teenager's behavior is still incompletely understood by parents.
be universally/widely understood